File level backup and block level backup are two techniques employed by computer systems to make additional copies of data. If a data loss event occurs, these additional copies may be used to restore the data. During an initial file level backup, individual files are copied from a primary storage device to a secondary storage device. After the initial backup, subsequent backups (also called incremental backups) only need to copy files from the primary storage device that were modified since the previous backup. In the event of a data loss event, data can be restored by copying the files from the secondary storage device to the primary storage device.
During an initial block level backup (also called an image backup), blocks from the primary storage device are copied to the secondary storage device. After the initial backup, subsequent incremental backups only copy blocks from the primary storage device that were modified since the previous backup. Block level backups are typically more efficient than file level backups since only the modified blocks are copied, not entire modified files.